The treasure trove of data provides a snapshot of life during the Great Depression.

During the 1930s, the Dust Bowl pushed many poverty-stricken Americans west in search of work and more productive farmlands.

Population declined by more than 25 percent in some rural counties of Oklahoma, Texas and Kansas. Clark County, Nevada, for example, nearly doubled in population to 16,000 people.

census.gov

California on the hand, grew substantially between 1930 and 1940. Los Angeles county gained more than half a million people — the largest increase in population of any county in that decade.

census.gov

Slate's Matthew Yglesias points out that population shifts during the Great Depression were more drastic than today's economic recession, in part because the standards of living were lower and people were more willing to move,as it was a matter of life and death:

Bad as the Depression was, it would have been even worse had people not had the opportunity to [move]. And by the same token, our current economic downturn would be less severe if people living in economically weak areas were more willing to drop everything and move to places where the job prospects are better.